Frequency-grouping arrangement for communication systems



July 10, 1928. 1,676,614

. R. A. HEISING FREQUENCY GROUPING ARRANGEMENT FOR COMMUNICATION SYSTEMS 'Filed Dec. 51, 1925 2 Sheets-Sheet 2 DKK /za I45 /N VE N TOR R4 VMU/VD ,4. fins/Na Arran/vy Patented July it), li l 'il l.

umrensT TEs PATENT tries-- RAYMOND A. HEISING,'OF MILLBURN, NEXV JERSEYiASSIGNOR TO "WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK N, Y., A CORPORATION OF NEW FREQUENCY-GROUPING ARRANGEMENT FOB COMMUNICATION SYSTEMS;

Application filed December 31, 1923. Serial No. 683,631.

This invention relates to grouping of frequencies for radio transmitting and receiving and is particularly adapted for use in connection with systems in which the incom- 5 ing waves are combined with transmitted waves to produce a beat frequency. More particularly the invention relates to Wave length arrangements adapted to provide many two-way channels for ship-to-shore 1"" connnunication, the channels being arranged to provide i'ninimuni interference between channels.

An object. of the invention is to provide for the utilization of a large number of fre- 1 quencies suitable for radio communication in connection with systems of the type in which incoming Waves and waves used in transmitting are-combined to :torm a wave of intermediate frequency.

More specifically an object of this invention is to provide a grouped arrangement of frequencies for two-way communication with the frequencies in none of the groups overlapping.

In systems embodying the invention terminal stations may be provided in sets to utilize the wave lengths of each group. Thus if a particular group involves three pairs of wave lengths, these will serve for three simultaneous non-interfering two-way communications without interfering with conversations upon wave lengths of the other groups. The shoreterminals for each group may comprise a group of channels of a mulfit) channels of individual systems located either cloie together or in the same general territory. 'In this specification individual systems will be' disclosed specifically. The shore terminals of other groups of channels are preterably located in regions somewhat remote fron'r each other. In the extreme caie all the shore terminals of each group may be located at the same radio plant.

Although particularly adapted for shipto-shore multiplex systems, the principles of. the invention are applicable to other systems in which the terminal stations are either tired or movable, or parttixed and rt movable.

The individual system;: which may be employed for carrying out the objects oi the invention may each comprise a transmitting set and receiving set for each channel at tiplex system or a corresponding group of each station. The transmitting set com-' prises a source of speech wave amplifying devices, a source ofhigh frequency waves, means for i'i'iodulating the high 'trequency waves and an antenna for radiating the modulated waves. The receiving set coinprises an. antenna for receiving incoming waves, a plurality of detectors a source of local. oscillations it such is necessary, and. a receiver torreciving audible notes or speech waves.

- A plurality of stations each with a different range "of frequencies vtor transmitting and receiving are so located and are arranged to employ such frequencies to prevent interference between stations. Each frequency maybe utilized bya separate in stall-ation, or may be utilized in a separate channel ot one installation. The beat. frequency produced by the combination of the incoming waves and Waves used in transmitting is different t'or each group of channels and the trequencics are so grouped that the combination of one used in transmitting by a ship station in one group with another used by a ship stationit'or transmittingqin a dlfl'erent group will produce'a beat frequency unlike that oi? either of the two groups and consequently the undesired beat frequency will be tuned out by the receiving apparatus of the various channels of the 1 two groups.

For a more definite explanation of the invention, reference is madeto the accompanying drawings inwhich:

Fig. 1 represents a pluralit of groups of pairs of frequencies for transmitting and re.- ceiving, each. group having the pairs so arranged as to produce a beat frequency ditterent from beat frequencies of other Fig. 2 reprezents a circuit diagram'ot a transmitting and receiving circuit constituting a single two-way channel;

Fig. 3 represents a transmittingand receiving circuit thereceiving circuit making use of locally produced oscillations for stepping down or beatingdown the beat frequency in case it is too high for selection by conveniently designed selective circuits; and

Fig. 4 is a diagrammatic representation of the relation of frequencies and -geographical positioning in the system of the invention. I

Fig. l represents six similar groups 0 kilocycles inclusive.

of the corresponding transmitting and re' ceiving frequency waves produce a beat frequency of 25 kilocycles, which may be detected and the resultant audible note received by telephone. receivers. Any difference frequency heat produced by non corresponding pairs of frequencies of Group 1 will be readily separable from a 25 kilocycle beat frequency. Group .2 is a group of channels transmitting frequencies ranging from 150 to 170 kilocycles inclusive, and receiving frequencies ranging from 180 to 200-kilocycles inclusive, with abeat frequency of30 kilocycles. Group 3 comprises five channels with transmitting frequencies ranging from 210 to 250 kilocycles inclusive, and receiving frequencies from 230 to 300 For this group the beat frequency is 50 kilocycles. Group 4 contains siX channe-ls with frequencies rang ing from 310 to 360 kilocycles inclusive, for transmitting, and 380 to 430 kilocycles 1nclusive, for receiving. In this. group the beat frequency is 70 kilocycles. Group 5 has a beat frequency of 100 kilocycles and frequencies ranging from 440 to kilocycles inclusive, for transmitting and 540 to 630. kilocycles inclusive for receiving. In Group 6 the frequencies range from 640 to 790 kilocycles inclusive, for transmitting, and from-800 to 950 kilocycles inclusive, for receiving. The beat frequency in this case is 160 kilocycles. i

Fig. 4discloses a typical frequency and geographical layout of the invention. The particular frequencies disclosed in this fig ure were, for convenience, made the same. as those indicated inFig. 1, only the freqencies of Groups 1, 2 and 3 actually being indicated. by label. It is a particular purpose of this figure to show any relation of the frequency allocation to geographical distribution whereby there is made possible a compensation for acondition of frequency spacing which under other circumstances would be too small, by the device of a greater geographical spacing of the stations which, under these conditions, tend to interfere. The principle of this compensating operation willbe explained in the later description of the operation of the invention.

Fig. 2 represents a transmitting and receiving system using two antennae and employing the method of combining waves of a transmitting frequency with the'incoming waves to produce a beat frequency. Voice frequency waves are supplied to the voice frequency amplifying device 13 from the circuit 18, which includes microphone 10 and source of direct current 11, by means of transformer 12. The microphone circuit typifies any source of low frequency or signaling waves such as a telephone line. Ainplifying device 13 maybe any of. the coin ventional types, such as that disclosed by patent to Scriven, 1,459,419, June 19, 1923. High frequency.carrier waves are supplied by a source 14 and are impressed upon a modulating device 15 along with amplified speech waves from amplifier 13. Modulater 15 maybe of any well known type, such as that disclosed in the patent to Van der Bijl, 1,350,752, August 24, 1920. Modulated. high frequency waves are supplied to the antenna circuit including the induction coil. 16 and hence are radiated from aerial 17. Incoming waves are received by selecting waves of the frequency to be 'detected, The incoming waves are impressed on the detector along with waves of the carrier frequency wave used in transmitting and a resultant beat frequency wave is produced. Tuned circuit 26 comprising inductance 27 and capacity 28 and the tuned circuit 29 comprising inductance 30 and capacity 31 select the waves to be received. Such waves are then finally detectedby the detector 32 and received by the receiver 33. Amplifying devices, if such are needed, may be supplied.

Fig. 3 represents a receiving system employing double detection to be used in a system involving this methodof grouping frequencies. Transmitting is carried on in a manner similar .to that shownin Fig. 2. Modulated waves from the source 34 are impressed upon the antenna 36 by means of induction coils which act as a transformer. Incoming waves reach the antenna 37, pass through tuned circuit 38 comprising inductance 39 and capacity 40, through tuned circuit 41 which comprises inductance 42 and capacity 43, to ground. Coil 45 of tuned circuit 44 is inductively coupled to coil 42. Capacity 46 completes tuned circuit 44. Incoming waves and waves of the carrier frequency used in transmitting which are also received by the antenna 37 are impressed upon the high frequency detector 47 and a resultantbeat frequency.obtained.

This beat frequency wave is selected by tuned circuit 48 made up of inductance 49 and capacity 50 and by the tuned circuit 64 made up of inductance 51 and capacity 54 and is transmitted to the intermediate frequency detector'55. Local oscillations to beat with the wave of the intermediate frequency are supplied. to the intermediate frequency detector 55 by local oscillator. 53 through innote received by the receiver 63 as in Fig.

2. If amplifying devices are needed such may be supplied at any point in the circuit.

Operation.

In operation, first considering Group 1' of Fig. 1, waves of frequencies of 1,00, and kilocycles are used for transmitting from a given station, while those of 125, and kilocycles are used for receiving at the same station. Transmitting wave frequencies may be used in connection with separate sets or may be the channels of one set. In either case they are usually located. at a central point, which in ship-to-shore communication will be a land station. The waves of frequencies used in receiving will in this case be transmitted from ships at sea with which communication is carried on by a land station. In the absence of predetern'nned assignment of frequencies the shore StfltlOIl may signal the ship and indlcate 'Wl'llCh frequency the ship 15 to use for transmission and reception. For'example, the shore st-a-.

tion will transmit over 100 ki'locycles frequency and the ship over 125 kilocycles frequency. The incoming waves and the waves used in transmitting will be impressed simultaneously upon the detector 25 of such a receiving circuit as shown in Fig. 2. The beatfrequency will be 25 kilocycles and will be selected-by the tuned circuits 26 and 29 resonant at that frequency and impressed upon the detector 32 and the resultant audible notereceived by receiver A [ship station sending over the'125 kilocyele wave will have a beat note of 25 kil ocycles when receiving, both with the station sending over the 100 kilocycle wave and the one sending over the kilocycle wave of Group 2. By means of tuned circuit the waves from the 150 kilocycle station can be tuned out and only the 100 kilocycle waves detected. The selective action of circuit 22 is facilitated by the fact that the shore stations of Group 2 will be spaced. at some little distance from the shore stations of Group 1, hence when a ship is in the zone of the shore stations of Group 1, the energy of the 150 kilocycle wave from a station of Group 2, arriving at the ship will be relatively feeble. The frequencies are grouped in such a manner that each group may'represent a station located on different points along the coast for communication rwith .ships, the larger groups being stations through which. the greatest traffic passes. These stations will be located far enough apart to prevent interference with each other. In Groups 5 and 6 in which the beat frequency is 100 kilocycles and kilocycles, it may be advisable to supply oscil lations 'tobeat' with such beat frequencies. In this manner an intermediate frequency is produced, which can readily be selected from interfering Wave components and detected. With reference'to Fig. 3 incoming Waves reach the antenna 37, pass through tuned circuits 38, 1-1 and lt to the detector 47 where they'are combined with waves of the carrier frequencies used in transmitting. The beat frequency obtained in this manner passes through tuned circuits 4:8 and (Vito the detector 55 along with oscillations from the local oscillator 53. The combination of diate frequency which isv selected by tuned circuits 56 and 59, impressed upon detector 62 and the resultant note is received by receiver r r i l Each group has a beat frequency entirely different from the other groups, which facilitates selection of the'prop'er messages for reasons hereinafter stated. Should a ship station sending over one frequency in one group receive a message sent-by a. ship station in a different group, the beat frequency between the two'would be a frequency different from that of either of the two groups, and it would consequently be tuned out by the intermediate frequency tuned circuits provided for that purpose.

Consequently the present invention provides a multiplex ship-to-shore or other com munication system in which a maximum number of channel-s can be operated with a minimum of interference. A high degree tures:- V q 1 (1) Individual channels of one group of land stations employ such outgoing frequencies and such an intermediate frequency that undesired outgoing frequencies cannot produce beats of the intermediate frequency.

(2) Land stations of different groups which employ such outgoing frequencies that they might beat together to produce an intermediate frequency employed by either of said groups are so widely separated that high frequency selectionis sufficient to prevent interference.

(3) Waves of frequencies outgoingfrom land stations of different groups 'or the same group arriving at a. land station of still another group will be of energies so feeble that high frequency selection-is sufficient to the prevent interference even though the frequencies differ by the intermediate frequency of land stations at which they'arrive.

(4) Outgoing waves from two ship stations of any group or groups combining at a land station of any other group to produce waves of the intermediate frequency of that group will be of energy so feeble that high frequency selection will suffice.

(5) Waves of ship stat-ions of the same group cannot produce waves of the intermediate frequency of that group. Within the group therefore both high and intm'n'lcdiate frequency selectivity will conspire to prevent interference. 1

(6) l Vavcs outgoing from ship stations of the same-or different groups arriving at any ship station having an intermediate frequency equal to the difierence of the frequencies of the arriving waves will be so feeble that high frequency selectivity will suflice. v

(7) Selectivity will be greatly increased by the fact that energy ofthe :local outgoing carrier frequency at any station will in general be of much greaterintensity than the energy of any wave arriving from a distant station. Waves of the desired incoming frequency will, therefore, be reinforced disproportionatelyto any reinforcement of undesired waves which may incidentally occur.

(8) In addition to "the use of special separation, Ehigh, frequency selectivity, and one or more stages of lower frequency selectivity, other known means such as directive transmission and receptive antenna. may be employed in a manner and with effects Well known. I v

The use of the grouping of frequencies and stations set forth hereinis not limited in application to diflerence frequency or other duplex systems but may be employed in connection with other systems as will be apparent to those skilled in the art.

Furthermore the invention is not limited in application tofrequency spacings of 10 kilocycles nor to the same frequency spacing of all the channels in each group or the same spacing or plan of spacing forthe several groups. I In atypical system, for example, such as would cover the'Atlantic seaboard of the United States the various groups of shore stations might be distributed at points along the coast such as Maine, Long Island, Delaware, Virginia, Florida and Texas. Each of thesestations could be connected with the continental land line system and interconnected with each other to facilitate communication between any ship and any subscriber on land by a channel of a group of channels having termini nearestthe ship.

The present invention is not limited in application to use wlth difference frequency duplex systems of any particular kind or to use with circuits for transmission andrecepof wave. frequencies and-comprising one or more pairs of twoavay channels corresponding to the frequency groups, said groups being so physically related as to tend to in ierferc-i, means for transmitting a wave of one frequency from each portion in opposite directions to constitute a two-way channel, and means for receiving each said transmitted. Wave and combining it with the locally transmitted Wave to produce a difference frequency wave, the difference between the frequencies of the pairs of waves for the two-way channels of each group being con stant within each group, which constant amount differs for each groupi i 2. A radio system comprising apparatus for operating a plurality of groups of transmission channels, each group being located in a region more or less geographically distinct from the regions of the other-groups but so related that waves from a. channel of one group are incident on the receiving circuits of other groups, each group comprising one or more two-Way channels each employing oppositely directed frequencies differmg by a constant amount within-the group,

ing a range individual thereto, said 'requencies being assigned in such a manner,

and the geographical spacing. of the channels being such, that there is a relatively large frequency discrimination, both primary and secondary, .against interfering Waves originating at the nearest stations, and that the waves against which there is relatively small. frequency discrimination,

either primary or secondary, originate -.at

more distant stations.

4E. The system of claim 3 in which the spacing between the frequencies of a pair is the same for all pairs in a group and differout for different groups.

5. A radio system comprising a pluralityfrequency wave, the intermediate frequency being the same for all the two-way channels in a group, the minimum frequency dif ference between waves transmitted in the same direction in different groups differing from the closest intermediate frequency of a group by a less amount than the similar difference between waves transmitted in the same direction in said group, each halfgroup of receiving circuits being adapted to receive from the nearest. half-group of transmitting circuits, and the physical relation of the groups of channels being similar to the corresponding relation of their frequencles.

6. A radio system comprising a plurality of groups of one or more two-way channels, the one-way channels of each group corresponding to each direction occupying an individual frequency range and constituting a half-group, the resultant series of halfgroups in the frequency range as a whole being staggered with respect to the direc tions of transmission, each receiving circuit being of the double selective type comprising means for combining the incoming and outgoing waves to produce an intermediate fre-- the intermediate frequency quency wave,

for all the two-way channels being the same .ina group, the physical relation of the groups of channels being similar to the corresponding relation of their frequencies, the frequency difference between each two oppositely directed one-way channels of eachgroup differing from the intermediate frequency of an adjacent group by a less amount than the difference between the frequencies of adjacent one-way channels in either group, and each half-group of receiving circuits being adapted tojreceive from the nearest group of transmitting circuits.

7. A radio system comprising a plurality of groups of one or more two-way channels, the one-way channels of each group corresponding to each direction occupying an individual frequency, range and constituting a halfgroup, the resultant series of half-groups in the frequency range as a whole being staggored with respect to the directions of trans mission, each receiving circuit being of the double selective type comprising means for combining the incomin and outgoing waves to produce an intermediate frequency wave, the intermediate frequency being the same for all the two-way channels in a group, the minimum frequency difierence between waves transmitted in the same direction in different groups differing from the closest intermediate frequency of a group by a less amount than the similar difference between waves transmitted in the same direction in said group, the frequency difference between each two oppositely directed one-way channels of each group differing from the intermediate fre qucncy of an, adjacent group by a less amount than the difference between the frequencies of adjacent one-way channels in either group, each half-group of receiving circuits being adapted to receive from the nearest half-group of transmitting circuits, and the physical relation of the groups of channels being similar to the corresponding relation of their frequencies.

8. A radio system comprising a plurality of groups of one or more two-way channels,

the oneway channels of each group corresponding to each direction occupying an illdividual frequency range and constituting a half-group, the resultant series of halfgroups in the frequency range as a whole being staggered with respect to the directions of transmission, each receiving circuit being of a double-selective type comprising means for combining the incoming and outgoing waves to produce an intermediate frequency wave, the intermediate frequency being the same for all the two-way channels in a group, the minimum frequency difference, in the frequency arrangement as a whole, between waves transmitted in opposite directions and not belongingto a two.- way channel, differing from the nearest in termediate frequency by aless amount than the similar difference between waves transmitted in the same direction in the group including said nearest intermediate frequency, each half-group of receiving circuits being adapted to receive from the nearest halfgroup of transmitting circuits and the physical relation of the groups of channels being similar to the corresponding relation of their frequencies.

In witness whereof, I hereunto subscribe my name this 28 day of December, A. D.

' RAYMOND A. I-IEISING. 

